1. Field of the Invention
The present invention relates generally to an apparatus and method for inserting discrete articles into cartridges. More particularly, the present invention relates to an improved device and method for inserting staple drivers into surgical stapling cartridges.
2. Description of the Related Art
In the field of microsurgery, a surgical instrument having a cutting blade traverses a specific path through tissue. One feature of the surgical instrument is a single-use cartridge that is a holder for surgical staples. The cartridge is an elongated rectangular plastic body with a longitudinal channel, that serves as a guide for the surgical blade, having rows of small staples on opposite sides of the channel. The staples in the cartridge are aligned parallel to the guide channel. After the blade makes its cut, and other necessary surgical operations are performed, each side of the incision is stapled together to close the incision. In order to push the staples into the tissue adjacent the cartridge, drivers are inserted in the cartridge to push the staples out of the cartridge and through the tissue against an anvil on the opposing side of the surgical instrument as the cartridge, thereby deflecting the points of the staples into a clasping position.
There may be as many as fifty or more very small staples on each side of a two inch incision. Each staple can be driven simultaneously into the tissue to close the incision by the correspondingly small drivers. Insertion of the drivers into the cartridge and maintaining them in place to drive the staples into the tissue is a labor-intensive chore due to the small size of the drivers.
One prior art system for mounting the staple drivers into apertures, which are also called “pockets”, in the cartridge includes a plastic holder, commonly referred to as a “tree” having aligned “branches” with drivers integrally formed on an end of each of the aligned branches. The conventional cartridge is placed in an apparatus and the tree with the drivers is hand-manipulated to place the drivers adjacent the entrance to the pockets. This is normally accomplished by inserting the drivers in funnel-shaped passages that are aligned with the pockets. Each driver is subsequently driven into the associated pocket of the cartridge. The separation of the individual drivers from the branch of the tree on which it is mounted is accomplished by flexing the branches of the tree manually to break the tree away from the staple drivers. Then, a hand-manipulated tool is used to press each staple driver down into the cartridge to near the pocket opening on the opposite side of the cartridge.
Unfortunately, the finger operation of pressing each driver into a pocket, the flexing of the branches and the subsequent pressing from the hand-operated prongs can misalign some of the drivers within the pockets. Furthermore, the sizes of the pockets and the drivers vary slightly due to the minute structure involved and the fact that both the cartridge and the staple drivers are formed of thermoplastic resin, which does not always result in a perfectly formed structure. This combination of factors can cause some “play” in the assembly, which can result in an alignment problem. In particular, inversion of the cartridge after assembly can result in some of the drivers being displaced from their pockets. If a staple driver is absent, no staple will be driven into the tissue at that point in the incision.
Another problem with the assembly is that of misalignment of the drivers with the cartridge. The drivers are inserted into the funnel-shaped passages on the fixture so as to align each individual driver with an associated pocket on the cartridge. However, the funnel-shaped passages do not fully cure the misalignment problem. Because the funnels do not fully engage the driver to be inserted, there is commonly some misalignment.
The misalignment of the driver within the pocket can cause additional problems. If the driver is not properly aligned, the staple which is ejected by use of the staple driver may be inaccurately bent during the surgery. In addition, the misalignment of the staple driver in the pocket can increase the force needed to eject a staple or prevent the ejection of that staple entirely.
Yet another problem is the imprecision in the process of separating the staple drivers from the branches of the plastic “tree”, a process referred to as “degating.” The drivers are mounted to the tree prior to insertion in the cartridge, but must be removed from the tree before or during the insertion process. Because the separation of a driver from the tree is not precise, it leaves some material on one side of each driver. The remnants of material left on the drivers is not a predictable size, and often the remnants are larger than desired. While it is not practical to remove all of the holder material from the side of each driver in the separation process, it is important that the amount of material left on each driver be relatively consistent between drivers. This is because the material left on the side tends to cause friction when the staple driver is used in surgery. If the amount of material left is consistent, it allows a user of such a staple cartridge to accurately predict the amount of force needed to expel a staple in surgery. In addition, the smaller the volume of material left, the less friction will be generated, and the less the force required to use the staple cartridge.
It is known in the prior art to insert drivers mechanically into surgical stapling cartridges, as shown in U.S. Pat. No. 5,836,147 to Schnipke, U.S. Pat. No. 5,635,928 to Schnipke, and U.S. Pat. No. 6,158,205 to Schnipke et al., all of which are incorporated herein by reference. These machines require people to position the cartridges and the holders that contain the drivers, and actuate the machine to insert the tiny drivers into the pockets in the cartridges. After a fraction of the total number of drivers is inserted by one machine, the cartridge is then manually transported to the next machine, which inserts another fraction of the drivers.
If any drivers are improperly inserted into a cartridge, or are not inserted, the cartridge is either discarded or repaired. Thus, errors in insertion of the tiny parts can result in wasted time and/or product.
Even the machines disclosed and claimed in the patents referenced above, although representing a significant improvement over the prior art, have problems, especially regarding ongoing maintenance. For example, it is difficult and costly to sharpen the knives that sever the drivers from the plastic trees. These knives are unitary parts of the degating plates that align the drivers over the apertures in the cartridge into which the drivers are driven, which means that any removal for sharpening means the degating apparatus must be removed. After removal and sharpening of the knives, the degating plates must be realigned with the entire machine, and this can be time-consuming and inexact.
In U.S. Pat. No. 6,729,119 to Schnipke et al., which is incorporated herein by reference, a robotic loader is discussed for use in filling the cartridges discussed herein. However, this patent does not address the maintenance issues that continue to exist on the non-robotic devices discussed above.
Therefore, there is a need for an improved machine and method for loading drivers into surgical cartridges.